(1) Field of the Invention
The present invention generally relates to a projector, more particularly to a projector with a means of controlling the focal length of a zoom lens.
(2) Description of the Prior Art
Please refer to FIG. 1 and FIG. 2, which show a conventional projector 2. The conventional projector 2 has a zoom lens 8, a front end of a case 4 of the projector 2 has a hole, and the zoom lens 8 of the projector 2 extends toward outside the projector 2 from an interior of the case 4 via the hole.
A zoom rod 802 extends upward from a lateral of a column of the zoom lens 8. To move the zoom rod 802 is able to regulate the movement of a zoom lens set (not shown in figures) of the zoom lens 8 in order to adjust the focal length of the zoom lens 8.
A rectangular opening 402 is disposed on an upper surface of the case 4, wherein two long sides of the opening 402 extend and are parallel to two long sides of the case 4. An interior arc surface of a zoom ring 6 female-connects to a cylindrical lateral of the zoom lens 8, and the zoom ring 6 is disposed between the opening 402 and the zoom lens 8.
The interior the arc surface of the zoom ring 6 further has a groove, and a zoom rod 802 reciprocates along the groove. The zoom rod 802 is moved by moving the zoom ring 6 along the arc surface thereof in order to regulate the focal length of the zoom lens 8.
Furthermore, a handle 602 is disposed on an upper surface of the zoom ring 6, and passes through the opening 402 so as to reach an outside of the projector 2. Hence, a user changes the focal length of the zoom lens 8 by moving the handle 602 simply.
However, the opening 402 is shielded by the arc surface of the zoom ring 6, and there is a chink existed between an even surface of the case 4 and the arc surface of the zoom ring 6. The light in the projector 2 is leaked out and dust is deposited into the projector 2 from the chink. Hence, problems, such as light leakage and dust contamination occur.
Additionally, the handle 602 moves along the arc surface and passes through the opening 402. The handle 602 is fully extended out of the opening 402 when the handle 602 is moved at a middle of the opening 402, and the handle 602 is partly extending out of the opening when the handle 602 is moved at two ends of the opening 402. So that the handle 602 is not easy to operate for a user.